System of implantable devices for monitoring and/or affecting body parameters

ABSTRACT

A system for monitoring and/or affecting parameters of a patient&#39;s body and more particularly to such a system comprised of a system control unit (SCU) and one or more other devices, preferably battery-powered, implanted in the patient&#39;s body, i.e., within the envelope defined by the patient&#39;s skin. Each such implanted device is configured to be monitored and/or controlled by the SCU via a wireless communication channel. In accordance with the invention, the SCU comprises a programmable unit capable of (1) transmitting commands to at least some of a plurality of implanted devices and (2) receiving data signal from at least some of those implanted devices. In accordance with a preferred embodiment, the system operates in closed loop fashion whereby the commands transmitted by the SCU are dependent, in part, on the content of the data signals received by the SCU. In accordance with the invention, a preferred SCU is similarly implemented as a device capable of being implanted beneath a patient&#39;s skin, preferably having an axial dimension of less than 60 mm and a lateral dimension of less than 6 mm. Wireless communication between the SCU and the implanted devices is preferably implemented via a modulated sound signal, AC magnetic field, RF signal, or electric conduction.

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/042,447 filed Mar. 27, 1997 and U.S. patentapplication Ser. No. ______, filed Feb. 25, 1998 entitled“Battery-Powered Patient Implantable Device” which in turn claims thebenefit of U.S. Provisional Application No. 60/039,164 filed Feb. 26,1997.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to systems for monitoring and/oraffecting parameters of a patient's body for the purpose of medicaldiagnosis and/or treatment. More particularly, systems in accordancewith the invention are characterized by a plurality of devices,preferably battery-powered, configured for implanting within a patient'sbody, each device being configured to sense a body parameter, e.g.,temperature, O₂ content, physical position, etc., and/or to affect aparameter, e.g., via nerve stimulation.

[0003] Applicants' parent application Ser. No. ______, entitled “BatteryPowered Patient Implantable Device”, incorporated herein by reference,describes devices configured for implantation within a patient's body,i.e., beneath a patient's skin, for performing various functionsincluding: (1) stimulation of body tissue, (2) sensing of bodyparameters, and (3) communicating between implanted devices and devicesexternal to a patient's body.

SUMMARY OF THE INVENTION

[0004] The present invention is directed to a system for monitoringand/or affecting parameters of a patient's body and more particularly tosuch a system comprised of a system control unit (SCU) and one or moredevices implanted in the patient's body, i.e., within the envelopedefined by the patient's skin. Each said implanted device is configuredto be monitored and/or controlled by the SCU via a wirelesscommunication channel.

[0005] In accordance with the invention, the SCU comprises aprogrammable unit capable of (1) transmitting commands to at least someof a plurality of implanted devices and (2) receiving data signals fromat least some of those implanted devices. In accordance with a preferredembodiment, the system operates in closed loop fashion whereby thecommands transmitted by the SCU are dependent, in part, on the contentof the data signals received by the SCU.

[0006] In accordance with a preferred embodiment, each implanted deviceis configured similarly to the devices described in Applicants' parentapplication Ser. No. ______, and typically comprises a sealed housingsuitable for injection into the patient's body. Each housing preferablycontains a power source having a capacity of at least 1 microwatt-hour,preferably a rechargeable battery, and power consuming circuitrypreferably including a data signal transmitter and receiver andsensor/stimulator circuitry for driving an input/output transducer.

[0007] In accordance with a significant aspect of the preferredembodiment, a preferred SCU is also implemented as a device capable ofbeing injected into one patient's body. Wireless communication betweenthe SCU and the other implanted devices can be implemented in variousways, e.g., via a modulated sound signal, AC magnetic field, RF signal,or electrical conduction.

[0008] In accordance with a further aspect of the invention, the SCU isremotely programmable, e.g., via wireless means, to interact with theimplanted devices according to a treatment regimen. In accordance with apreferred embodiment, the SCU is preferably powered via an internalpower source, e.g., a rechargeable battery. Accordingly, an SCU combinedwith one or more battery-powered implantable devices, such as thosedescribed in the parent application, form a self-sufficient system fortreating a patient.

[0009] In accordance with a preferred embodiment, the SCU and otherimplanted devices are implemented substantially identically, beingcomprised of a sealed housing configured to be injected into thepatient's body. Each housing contains sensor/stimulator circuitry fordriving an input/output transducer, e.g., an electrode, to enable it toadditionally operate as a sensor and/or stimulator.

[0010] Alternatively, the SCU could be implemented as an implantable butnon-injectable housing which would permit it to be physically largerenabling it to accommodate larger, higher capacity components, e.g.,battery, microcontroller, etc. As a further alternative, the SCU couldbe implemented in a housing configured for carrying on the patient'sbody outside of the skin defined envelope, e.g., in a wrist band.

[0011] In accordance with the invention, the commands transmitted by theSCU can be used to remotely configure the operation of the otherimplanted devices and/or to interrogate the status of those devices. Forexample, various operating parameters, e.g., the pulse frequency, pulsewidth, trigger delays, etc., of each implanted device can be controlledor specified in one or more commands addressably transmitted to thedevice. Similarly, the sensitivity of the sensor circuitry and/or theinterrogation of a sensed parameter, e.g., battery status, can beremotely specified by the SCU.

[0012] In accordance with a significant feature of the preferredembodiment, the SCU and/or each implantable device includes aprogrammable memory for storing a set of default parameters. In theevent of power loss, SCU failure, or any other catastrophic occurrence,all devices default to the safe harbor default parameters. The defaultparameters can be programmed differently depending upon the conditionbeing treated. In accordance with a further feature, the system includesa switch preferably actuatable by an external DC magnetic field, forresetting the system to its default parameters.

[0013] In an exemplary use of a system in accordance with the presentinvention, a patient with nerve damage can have a damaged nerve“replaced” by an implanted SCU and one or more implanted sensors andstimulators, each of which contains its own internal power source. Inthis exemplary system, the SCU would monitor a first implanted sensorfor a signal originating from the patient's brain and responsivelytransmit command signals to one or more stimulators implanted past thepoint of nerve damage. Furthermore, the SCU could monitor additionalsensors to determine variations in body parameters and, in a closed loopmanner, react to control the command signals to achieve the desiredtreatment regimen.

[0014] The novel features of the invention are set forth withparticularity in the appended claims. The invention will be bestunderstood from the following description when read in conjunction withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a simplified block diagram of the system of the presentinvention comprised of implanted devices, e.g., microstimulators,microsensors and microtransponders, under control of an implanted systemcontrol unit (SCU);

[0016]FIG. 2 comprises a block diagram of the system of FIG. 1 showingthe functional elements that form the system control unit and implantedmicrostimulators, microsensors and microtransponders;

[0017]FIG. 3A comprises a block diagram of an exemplary implanteddevice, as shown in the parent application, including a battery forpowering the device for a period of time in excess of one hour inresponse to a command from the system control unit;

[0018]FIG. 3B comprises a simplified block diagram of controllercircuitry that can be substituted for the controller circuitry of FIG.3A, thus permitting a single device to be configured as a system controlunit and/or a microstimulator and/or a microsensor and/or amicrotransponder;

[0019]FIG. 4 is a simplified diagram showing the basic format of datamessages for commanding/interrogating the implanted microstimulators,microsensors and microtransponders which form a portion of the presentinvention;

[0020]FIG. 5 shows an exemplary flow chart of the use of the presentsystem in an open loop mode for controlling/monitoring a plurality ofimplanted devices, e.g., microstimulators, microsensors;

[0021]FIG. 6 shows a flow chart of the optional use of a translationtable for communicating with microstimulators and/or microsensors viamicrotransponders;

[0022]FIG. 7 shows a simplified flow chart of the use of closed loopcontrol of a microstimulator by altering commands from the systemcontrol unit in response to status data received from a microsensor;

[0023]FIG. 8 shows an exemplary injury, i.e., a damaged nerve, and theplacement of a plurality of implanted devices, i.e., microstimulators,microsensors and a microtransponder under control of the system controlunit for “replacing” the damaged nerve;

[0024]FIG. 9 shows a simplified flow chart of the control of theimplanted devices of FIG. 8 by the system control unit;

[0025] FIGS. 10A and 10BD show two side cutaway views of the presentlypreferred embodiment of an implantable ceramic tube suitable for thehousing the system control unit and/or microstimulators and/ormicrosensors and/or microtransponders;

[0026]FIG. 11 illustrates an exemplary battery suitable for powering theimplantable devices which comprise the components of the presentinvention; and

[0027]FIG. 12 shows an exemplary housing suitable for an implantable SCUhaving a battery enclosed within that has a capacity of at least 1watt-hour.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The present invention is directed to a system for monitoringand/or affecting parameters of a patient's body and more particularly tosuch a system comprised of a system control unit (SCU) and one or moredevices implanted in a patient's body, i.e., within the envelope definedby the patient's skin. Each such implantable device is configured to bemonitored and/or controlled by the SCU via a wireless communicationchannel.

[0029] In accordance with the invention, the SCU comprises aprogrammable unit capable of (1) transmitting commands to at least someof a plurality of implanted devices and (2) receiving data signals fromat least some of those implanted devices. In accordance with a preferredembodiment, the system operates in closed loop fashion whereby thecommands transmitted by the SCU are dependent, in part, on the contentof the data signals received by the SCU.

[0030] In accordance with a preferred embodiment, each implanted deviceis configured similarly to the devices described in Applicants' parentapplication Ser. No. ______ and typically comprises a sealed housingsuitable for injection into the patient's body. Each housing preferablycontains a power source having a capacity of at least 1 microwatt-hour,preferably a rechargeable battery, and power consuming circuitrypreferably including a data signal transmitter and receiver andsensor/stimulator circuitry for driving an input/output transducer.

[0031]FIG. 1 (essentially corresponding to FIG. 2 of the parentapplication) and FIG. 2 show an exemplary system 300 made of implanteddevices 100, preferably battery powered, under control of a systemcontrol unit (SCU) 302, preferably also implanted beneath a patient'sskin 12. As described in the parent application, potential implanteddevices 100 (see also the block diagram shown in FIG. 3A) includestimulators , e.g., 100 a, sensors e.g., 100 c, and transponders, e.g.,100 d. The stimulators, e.g., 100 a, can be remotely programmed tooutput a sequence of drive pulses to body tissue proximate to itsimplanted location via attached electrodes. The sensors, e.g., 100 c,can be remotely programmed to sense one or more physiological orbiological parameters in the implanted environment of the device, e.g.,temperature, glucose level, O₂ content, etc. Transponders, e.g., 100 d,are devices which can be used to extend the interbody communicationrange between stimulators and sensors and other devices, e.g., aclinician's programmer 172 and the patient control unit 174. Preferably,these stimulators, sensors and transponders are contained in sealedelongate housing having an axial dimension of less than 60 mm andlateral dimension of less than 6 mm. Accordingly, such stimulators,sensors and transponders are respectively referred to asmicrostimulators, microsensors, and microtransponders. Suchmicrostimulators and microsensors can thus be positioned beneath theskin within a patient's body using a hypodermic type insertion tool 176.

[0032] As described in the parent application, microstimulators andmicrosensors are remotely programmed and interrogated via a wirelesscommunication channel, e.g., modulated AC magnetic, sound (i.e.,ultrasonic), RF or electric fields, typically originating from controldevices external to the patient's body, e.g., a clinicians's programmer172 or patient control unit 174. Typically, the clinician's programmer172 is used to program a single continuous or one time pulse sequenceinto each microstimulator and/or measure a biological parameter from oneor more microsensors. Similarly, the patient control unit 174 typicallycommunicates with the implanted devices 100, e.g., microsensors 100 c,to monitor biological parameters. In order to distinguish each implanteddevice over the communication channel, each implanted device ismanufactured with an identification code (ID) 303 specified in addressstorage circuitry 108 (see FIG. 3A) as described in the parentapplication.

[0033] By using one or more such implantable devices in conjunction withthe SCU 302 of the present invention, the capabilities of such implanteddevices can be further expanded. For example, in an open loop mode(described below in reference to FIG. 5), the SCU 302 can be programmedto periodically initiate tasks, e.g., perform real time tasking, such astransmitting commands to microstimulators according to a prescribedtreatment regimen or periodically monitor biological parameters todetermine a patient's status or the effectiveness of a treatmentregimen. Alternatively, in a closed loop mode (described below inreference to FIGS. 7-9), the SCU 302 periodically interrogates one ormore microsensors and accordingly adjust the commands transmitted to oneor more microstimulators.

[0034]FIG. 2 shows the system 300 of the present invention comprised of(1) one or more implantable devices 100 operable to sense and/orstimulate a patient's body parameter in accordance with one or morecontrollable operating parameters and (2) the SCU, 302. The SCU 302 isprimarily comprised of (1) a housing 206, preferably sealed andconfigured for implantation beneath the skin of the patient's body asdescribed in the parent application in reference to the implanteddevices 100, (2) a signal transmitter 304 in the housing 206 fortransmitting command signals, (3) a signal receiver 306 in the housing206 for receiving status signals, and (4) a programmable controller 308,e.g., a microcontroller or state machine, in the housing 206 responsiveto received status signals for producing command signals fortransmission by the signal transmitter 304 to other implantable devices100. The sequence of operations of the programmable controller 308 isdetermined by an instruction list, i.e., a program, stored in programstorage 310, coupled to the programmable controller 308. While theprogram storage 310 can be a nonvolatile memory device, e.g., ROM,manufactured with a program corresponding to a prescribed treatmentregimen, it is preferably that at least a portion of the program storage310 be an alterable form of memory, e.g., RAM, EEPROM, etc., whosecontents can be remotely altered as described further below. However, itis additionally preferable that a portion of the program storage 310 benonvolatile so that a default program is always present. The rate atwhich the program contained within the program storage 310 is executedis determined by clock 312, preferably a real time clock that permitstasks to be scheduled at specified times of day.

[0035] The signal transmitter 304 and signal receiver 306 preferablycommunicate with implanted devices 100 using sound means, i.e.,mechanical vibrations, using a transducer having a carrier frequencymodulated by a command data signal. In a preferred embodiment, a carrierfrequency of 100 KHz is used which corresponds to a frequency thatfreely passes through a typical body's fluids and tissues. However, suchsound means that operate at any frequency, e.g., greater than 1 Hz, arealso considered to be within the scope of the present invention.Alternatively, the signal transmitter 304 and signal receiver 306 cancommunicate using modulated AC magnetic, RF, or electric fields.

[0036] The clinician's programmer 172 and/or the patient control unit174 and/or other external control devices can also communicate with theimplanted devices 100, as described in the parent application,preferably using a modulated AC magnetic field. Alternatively, suchexternal devices can communicate with the SCU 302 via a transceiver 314coupled to the programmable controller 308. Since, in a preferredoperating mode, the signal transmitter 304 and signal receiver 306operate using sound means, a separate transceiver 314 which operatesusing magnetic means is used far communication with external devices.However, a single transmitter 304/receiver 306 can be used in place oftransceiver 314 if a common communication means is used.

[0037]FIG. 3A comprises a block diagram of an exemplary implanted device100 (as shown in FIG. 2 of the parent application) which includes abattery 104, preferably rechargeable, for powering the device for aperiod of time in excess of one hour and responsive to command signalsfrom a remote device, e.g., the SCU 302. As described in the parentapplication, the implantable device 100 is preferably configurable toalternatively operate as a microstimulator and/or microsensor and/ormicrotransponder due to the commonality of most of the circuitrycontained within. Such circuitry can be further expanded to permit acommon block of circuitry to also perform the functions required for theSCU 302. Accordingly, FIG. 3B shows an alternative implementation of thecontroller circuitry 106 of FIG. 3A that is suitable for implementing amicrostimulator and/or a microsensor and/or a microtransponder and/orthe SCU 302. In this implementation the configuration data storage 132can be alternatively used as the program storage 310 when theimplantable device 100 is used as the SCU 302. In this implementation,XMTR 168 corresponds to the signal transmitter 304 and the RCVR 114 bcorresponds to the signal receiver 306 (preferably operable using soundmeans via transducer 138) and the RCVR 114 a and XMTR 146 correspond tothe transceiver 314 (preferably operable using magnetic means via coil116).

[0038] In a preferred embodiment, the contents of the program storage310, i.e., the software that controls the operation of the programmablecontroller 308, can be remotely downloaded, e.g., from the clinician'sprogrammer 172 using data modulated onto an AC magnetic field. In thisembodiment, it is preferable that the contents of the program storage310 for each SCU 302 be protected from an inadvertent change.Accordingly, the contents of the address storage circuitry 108, i.e.,the ID 303, is preferably used as a security code to confirm that thenew program storage contents are destined for the SCU 302 receiving thedata. This feature is significant if multiple patient's could bephysically located, e.g., in adjoining beds, within the communicationrange of the clinician's programmer 172.

[0039] In a further aspect of the present invention, it is preferablethat the SCU 302 be operable for an extended period of time, e.g., inexcess of one hour, from an internal power supply 316. While a primarybattery, i.e., a nonrechargeable battery, is suitable for this function,it is preferable that the power supply 316 include a rechargeablebattery, e.g., battery 104 as described in the parent application, thatcan be recharged via an AC magnetic field produced external to thepatient's body. Accordingly, the power supply 102 of FIG. 3A (describedin detail in the parent application) is the preferred power supply 316for the SCU 302 as well.

[0040] The battery-powered devices 100 of the parent invention arepreferably configurable to operate in a plurality of operation modes,e.g., via a communicated command signal. In a first operation mode,device 100 is remotely configured to be a microstimulator, e.g., 100 aand 100 b. In this embodiment, controller 130 commands stimulationcircuitry 110 to generate a sequence of drive pulses through electrodes112 to stimulate tissue, e.g., a nerve, proximate to the implantedlocation of the microstimulator, e.g., 100 a or 100 b. In operation, aprogrammable pulse generator 178 and voltage multiplier 180 areconfigured with parameters (see Table I) corresponding to a desiredpulse sequence and specifying now much to multiply the battery voltage(e.g., by summing charged capacitors or similarly charged batteryportions) to generate a desired compliance voltage V_(c). A first FET182 is periodically energized to store charge into capacitor 183 (in afirst direction at a low current flow rate through the body tissue) anda second FET 184 is periodically energized to discharge capacitor 183 inan opposing direction at a higher current flow rate which stimulates anearby nerve. Alternatively, electrodes can be selected that will forman equivalent capacitor within the body tissue. TABLE I StimulationParameters Current: continuous current charging of storage capacitorCharging currents: 1, 3, 10, 30, 100, 250, 500 μa Current Range: 0.8 to40 ma in nominally 3.2% steps Compliance Voltage: selectable, 3-24 voltsin 3 volt steps Pulse Frequency (PPS): 1 to 5000 PPS in nominally 30%steps Pulse Width: 5 to 2000 μs in nominally 10% steps Burst On Time(BON): 1 ms to 24 hours in nominally 20% steps Burst Off Time (BOF): 1ms to 24 hours in nominally 20% steps Triggered Delay to BON: eitherselected BOF or pulse width Burst Repeat Interval: 1 ms to 24 hours innominally 20% steps Ramp On Time: 0.1 to 100 seconds (1, 2, 5, 10 steps)Ramp Off Time: 0.1 to 100 seconds (1, 2, 5, 10 steps)

[0041] In a next operation mode, the battery-powered implantable device100 can be configured to operate as a microsensor, e.g., 100 c, that cansense one or more physiological or biological parameters in theimplanted environment of the device. In accordance with a preferred modeof operation, the system control unit 302 periodically requests thesensed data from each microsensor 100 c using its ID stored in addressstorage 108, and responsively sends command signals to microstimulators,e.g., 100 a and 100 b, adjusted accordingly to the sensed data. Forexample, sensor circuitry 188 can coupled to the electrodes 112 to senseor otherwise used to measure a biological parameter, e.g., temperature,glucose level, or O₂ content and provided the sensed data to thecontroller circuitry 106. Preferably, the sensor circuitry includes aprogrammable bandpass filter and an analog to digital (A/D) converterthat can sense and accordingly convert the voltage levels across theelectrodes 112 into a digital quantity. Alternatively, the sensorcircuitry can include one or more sense amplifiers to determine if themeasured voltage exceeds a threshold voltage value or is within aspecified voltage range. Furthermore, the sensor circuitry 188 can beconfigurable to include integration circuitry to further process thesensed voltage. The operation modes of the sensor circuitry 188 isremotely programable via the devices communication interface as shownbelow in Table II. TABLE II Sensing Parameters Input voltage range: 5 μvto 1 V Bandpass filter rolloff: 24 dB Low frequency cutoff choices: 3,10, 30, 100, 300, 1000 Hz High frequency cutoff choices: 3, 10, 30, 100,300, 1000 Hz Integrator frequency choices: 1 PPS to 100 PPS Amplitudethreshold 4 bits of resolution for detection choices:

[0042] Additionally, the sensing capabilities of a microsensor includethe capability to monitor the battery status via path 124 from thecharging circuit 122 and can additionally include using the ultrasonictransducer 138 or the coil 116 to respectively measure the magnetic orultrasonic signal magnitudes (or transit durations) of signalstransmitted between a pair of implanted devices and thus determine therelative locations of these devices. This information can be used todetermine the amount of body movement, e.g., the amount that an elbow orfinger is bent, and thus form a portion of a closed loop motion controlsystem.

[0043] In another operation mode, the battery-powered implantable device100 can be configured to operate as a microtransponder, e.g., 100 d. Inthis operation mode, the microtransponder receives (via theaforementioned receiver means, e.g., AC magnetic, sonic, RF or electric)a first command signal from the SCU 302 and retransmits this signal(preferably after reformatting) to other implanted devices (e.g.,microstimulators, microsensors, and/or microtransponders) using theaforementioned transmitter means (e.g., magnetic, sonic, RF orelectric). While a microtransponder may receive one mode of commandsignal, e.g., it may retransmit the signal in another mode, e.g.,ultrasonic. For example, clinician's programmer 172 may emit a modulatedmagnetic signal using a magnetic emitter 190 to program/command theimplanted devices 100. However, the magnitude of the emitted signal maynot be sufficient to be successfully received by all of the implanteddevices 100. As such, a microtransponder 100 d may receive the modulatedmagnetic signal and retransmit it (preferably after reformatting) as amodulated ultrasonic signal which can pass through the body with fewerrestrictions. In another exemplary use, the patient control unit 174 mayneed to monitor a microsensor 100 c in a patient's foot. Despite theefficiency of ultrasonic communication in a patient's body, anultrasonic signal could still be insufficient to pass from a patient'sfoot to a patient's wrist (the typical location of the patient controlunit 174). As such, a microtransponder 100 d could be implanted in thepatient's torso to improve the communication link.

[0044]FIG. 4 shows the basic format of an exemplary message 192 forcommunicating with the aforementioned battery-powered devices 100, allof which are preconfigured with an address (ID), preferably unique tothat device, in their identification storage 108 to operate in one ormore of the following modes (1) for nerve stimulation, i.e., as amicrostimulator, (2) for biological parameter monitoring, i.e., as amicrosensor, and/or (3) for retransmitting received signals afterreformatting to other implanted devices, i.e., as a microtransponder.The command message 192 is primarily comprised of a (1) start portion194 (one or more bits to signify the start of the message and tosynchronize the bit timing between transmitters and receivers, (2) amode portion 196 (designating the operating mode, e.g., microstimulator,microsensor, microtransponder, or group mode), (3) an address (ID)portion 198 (corresponding to either the identification address 108 or aprogrammed group ID), (4) a data field portion 200 (containing commanddata for the prescribed operation), (5) an error checking portion 202(for ensuring the validity of the message 192, e.g., by use of a paritybit), and (6) a stop portion 204 (for designating the end of the message192). The basic definition of these fields are shown below in Table III.Using these definitions, each device can be separately configured,controlled and/or sensed as part of a system or controlling one or moreneural pathways within a patient's body. TABLE III Message Data FieldsMODE ADDRESS (ID) 00 = Stimulator 8 bit identification address 01 =Sensor 8 bit identification address 02 = Transponder 4 bitidentification address 03 = Group 4 bit group identification addressData Field Portion Program/Stimulate = select operating mode Parameter/Preconfiguration Select = select programmable parameter in program modeor preconfigured stimulation or sensing parameter in other modesParameter Value = program value

[0045] Additionally, each device 100 can be programmed with a group ID(e.g., a 4 bit value) which is stored in its configuration data storage132. When a device 100, e.g., a microstimulator, receives a group IDmessage that matches its stored group ID, it responds as if the messagewas directed to its identification address 108. Accordingly, a pluralityof microstimulators, e.g., 100 a and 100 b, can be commanded with asingle message. This mode is of particular use when precise timing isdesired among the stimulation of a group of nerves.

[0046] The following describes exemplary commands, corresponding to thecommand message 192 of FIG. 4, which demonstrate some of the remotecontrol/sensing capabilities of the system of devices which comprise thepresent invention:

[0047] Write Command—Set a microstimulator/microsensor specified in theaddress field 198 to the designated parameter value.

[0048] Group Write Command—Set the microstimulators/microsensors withinthe group specified in the address field 198 to the designated parametervalue.

[0049] Stimulate Command—Enable a sequence of drive pulses from themicrostimulator specified in the address field 198 according topreviously programmed and/or default values.

[0050] Group Stimulate Command—Enable a sequence of drive pulses fromthe microstimulators within the group specified in the address field 198according to previously programmed and/or default values.

[0051] Unit Off Command—Disable the output of the microstimulatorspecified in the address field 198.

[0052] Group Stimulate Command—Disable the output of themicrostimulators within the group specified in the address field 198.

[0053] Read Command—Cause the microsensor designated in the addressfield 198 to read the previously programmed and/or default sensor valueaccording to previously programmed and/or default values.

[0054] Read Battery Status Command—Cause the microsensor designated inthe address field 198 to return its battery status.

[0055] Define Group Command—Cause the microstimulator/microsensordesignated in the address field 198 to be assigned to the group definedin the microstimulator data field 200.

[0056] Set Telemetry Mode Command—Configure the microtransponderdesignated in the address field 198 as to its input mode (e.g., ACmagnetic, sonic, etc.), output mode (e.g., AC magnetic, sonic, etc.),message length, etc.

[0057] Status Reply Command—Return the requested status/sensor data tothe requesting unit, e.g., the SCU.

[0058] Download Program Command—Download program/safe harbor routines tothe device, e.g., SCU, microstimulator, etc., specified in the addressfield 198.

[0059]FIG. 5 shows a block diagram of an exemplary open loop controlprogram, i.e., a task scheduler 320, for controlling/monitoring a bodyfunction/parameter. In this process, the programmable controller 308 isresponsive to the clock 312 (preferably crystal controlled to thuspermit real time scheduling) in determining when to perform any of aplurality of tasks. In this exemplary flow chart, the programmablecontroller 308 first determines in block 322 if is now at a timedesignated as T_(EVENT1) (or at least within a sampling error of thattime), e.g., at 1:00 AM. If so, the programmable controller 308transmits a designated command to microstimulator A (ST_(A)) in block324. In this example, the control program continues where commands aresent to a plurality of stimulators and concludes in block 326 where adesignated command is sent to microstimulator X (ST_(X)). Such asubprocess, e.g., a subroutine, is typically used when multiple portionsof body tissue require stimulation, e.g, stimulating a plurality ofmuscle groups in a paralyzed limb to avoid atrophy. The task scheduler320 continues through multiple time event detection blocks until inblock 328 it determines whether the time T_(EVENTM) has arrived. If so,the process continues at block 330 where, in this case, a single commandis sent to microstimulator M (ST_(M)). Similarly, in block 332 the taskscheduler 320 determines when it is the scheduled time, i.e.,T_(EVENT0), to execute a status request from microsensor A (SE_(A)). Isso, a subprocess, e.g., a subroutine, commences at block 334 where acommand is sent to microsensor A (SE_(A)) to request sensor data and/orspecify sensing criteria. Microsensor A (SE_(A)) does notinstantaneously respond. Accordingly, the programmable controller 308waits for a response in block 336. In block 338, the returned sensorstatus data from microsensor A (SE_(A)) is stored in a portion of thememory, e.g., a volatile portion of the program storage 310, of theprogrammable controller 308. The task scheduler 320 can be a programmedsequence, i.e., defined in software stored in the program storage 310,or, alternatively, a predefined function controlled by a table ofparameters similarly stored in the program storage 310. A similarprocess can be used where the SCU 302 periodically interrogates eachimplantable device 100 to determine its battery status.

[0060]FIG. 6 shows an exemplary use of an optional translation table 340for communicating between the SCU 302 and microstimulators, e.g., 100 a,and/or microsensors, e.g., 100 c, via microtransponders, e.g., 100 d. Amicrotransponder, e.g., 100 d, is used when the communication range ofthe SCU 302 is insufficient to reliably communicate with other implanteddevices 100. In this case, the SCU 302 instead directs a data message,i.e., a data packet, to an intermediary microtransponder, e.g., 100 d,which retransmits the data packet to a destination device 100. In anexemplary implementation, the translation table 340 contains pairs ofcorresponding entries, i.e., first entries 342 corresponding todestination addresses and second entries 344 corresponding to theintermediary microtransponder addresses. When the SCU 302 determines,e.g., according to a timed event designated in the program storage 310,that a command is to be sent to a designated destination device (seeblock 346), the SCU 302 searches the first entries 342 of thetranslation table 340, for the destination device address, e.g., ST_(M).The SCU 302 then fetches the corresponding second table entry 344 inblock 348 and transmits the command to that address. When the secondtable entry 344 is identical to its corresponding first table entry 342,the SCU 302 transmits commands directly to the implanted device 100.However, when the second table entry 344, e.g., T_(N), is different fromthe first table entry 342, e.g., ST_(M), the SCU 302 transmits commandsvia an intermediary microtransponder, e.g., 100 d. The use of thetranslation table 340 is optional since the intermediary addresses can,instead, be programmed directly into a control program contained in theprogram storage 310. However, it is preferable to use such a translationtable 340 in that communications can be redirected on the fly by justreprogramming the translation table 340 to take advantage of implantedtransponders as required, e.g., if communications should degrade andbecome unreliable. The translation table 340 is preferably contained inprogrammable memory, e.g., RAM or EPROM, and can be a portion of theprogram storage 310. While the translation table 340 can be remotelyprogrammed, e.g., via a modulated signal from the clinician's programmer172, it is also envisioned that the SCU 302 can reprogram thetranslation table 340 if the communications degrade.

[0061]FIG. 7 is an exemplary block diagram showing the use of the systemof the present invention to perform closed loop control of a bodyfunction. In block 352, the SCU 302 requests status from microsensor A(SE_(A)). The SCU 302, in block 354, then determines whether a currentcommand given to a microstimulator is satisfactory and, if necessary,determines a new command and transmits the new command to themicrostimulator A in block 356. For example, if microsensor A (SE_(A))is reading a voltage corresponding to a pressure generated by thestimulation of a muscle, the SCU 302 could transmit a command tomicrostimulator A (ST_(A)) to adjust the sequence of drive pulses, e.g.,in magnitude, duty cycle, etc., and accordingly change the voltagesensed by microsensor A (SE_(A)). Accordingly, closed loop, i.e.,feedback, control is accomplished. The characteristics of the feedback(position, integral, derivative (PID)) control are preferably programcontrolled by the SCU 302 according to the control program contained inprogram storage 310.

[0062]FIG. 8 shows an exemplary injury treatable by embodiments of thepresent system 300. In this exemplary injury, the neural pathway hasbeen damaged, e.g, severed, just above the a patient's left elbow. Thegoal of this exemplary system is to bypass the damaged neural pathway topermit the patient to regain control of the left hand. An SCU 302 isimplanted within the patient's torso to control plurality ofstimulators, ST₁-ST₃, implanted proximate to the muscles respectivelycontrolling the patient's thumb and fingers. Additionally, microsensor 1(SE₁) is implanted proximate to an undamaged nerve portion where it cansense a signal generated from the patient's brain when the patient wantshand closure. Optional microsensor 2 (SE₂) is implanted in a portion ofthe patient's hand where it can sense a signal corresponding tostimulation/motion of the patient's pinky finger and microsensor 3 (SE₃)is implanted and configured to measure a signal corresponding to grippressure generated when the fingers of the patient's hand are closed.Additionally, an optional microtransponder (T₁) is shown which can beused to improve the communication between the SCU 302 and the implanteddevices.

[0063]FIG. 9 shows an exemplary flow chart for the operation of the SCU302 in association with the implanted devices in the exemplary system ofFIG. 8. In block 360, the SCU 302 interrogates microsensor 1 (SE₁) todetermine if the patient is requesting actuation of his fingers. If not,a command is transmitted in block 362 to all of the stimulators(ST₁-ST₃) to open the patient's hand, i.e., to de-energize the muscleswhich close the patient's fingers. If microsensor 1 (SE₁) senses asignal to actuate the patient's fingers, the SCU 302 determines in block364 whether the stimulators ST₁-ST₃ are currently energized, i.e.,generating a sequence of drive pulses. If not, the SCU 302 executesinstructions to energize the simulators. In a first optional path 366,each of the stimulators are simultaneously (subject to formatting andtransmission delays) commanded to energize in block 366 a. However, thecommand signal given to each one specifies a different start delay time(using the BON parameter). Accordingly, there is a stagger between theactuation/closing of each finger.

[0064] In a second optional path 368, the microstimulators areconsecutively energized by a delay Δ. Thus, microstimulator 1 (ST₁) isenergized in block 368 a, a delay is executed within the SCU 302 inblock 368 b, and so on for all of the microstimulators. Accordingly,paths 366 and 368 perform essentially the same function. However, inpath 366 the interdevice timing is performed by the clocks within eachimplanted device 100 while in math 368, the SCU 302 is responsible forproviding the interdevice timing.

[0065] In path 370, the SCU 302 actuates a first microstimulator (ST₁)in block 370 a and waits in block 370 b for its corresponding muscle tobe actuated, as determined by microsensor 2 (SE₂), before actuating theremaining stimulators (ST₂-ST₃) in block 370 c. This implementationcould provide more coordinated movement in some situations.

[0066] Once the stimulators have been energized, as determined in block364, closed loop grip pressure control is performed in blocks 372 a and372 b by periodically reading the status of microsensor 3 (SE₃) andadjusting the commands given to the stimulators (ST₁-ST₃) accordingly.Consequently, this exemplary system has enabled the patient to regaincontrol of his hand including coordinated motion and grip pressurecontrol of the patient's fingers.

[0067] Referring again to FIG. 3A, a magnetic sensor 186 is shown. Inthe parent application, it was shown that such a sensor 186 could beused to disable the operation of an implanted device 100, e.g., to stopthe operation of such devices in an emergency situation, in response toa DC magnetic field, preferably from an externally positioned safetymagnet 187. A further implementation is disclosed herein. The magneticsensor 186 can be implemented using various devices. Exemplary of suchdevices are devices manufactured by Nonvolatile Electronics, Inc. (e.g.,their AA, AB, AC, AD, or AG series), Hall effect sensors, andsubminiature reed switches. Such miniature devices are configurable tobe placed within the housing of the disclosed SCU 302 and implantabledevices 100. While essentially passive magnetic sensors, e.g., reedswitches, are possible, the remaining devices include active circuitrythat consumes power during detection of the DC magnetic field.Accordingly, it is preferred that controller circuitry 302 periodically,e.g., once a second, provide power the magnetic sensor 186 and samplethe sensor's output signal 374 during that sampling period.

[0068] In a preferred implementation of the SCU 302, the programmablecontroller 308 is a microcontroller operating under software controlwherein the software is located within the program storage 310. The SCU302 preferably includes an input 376, e.g., a non maskable interrupt(NMI), which causes a safe harbor subroutine 378, preferably locatedwithin the program storage 310, to be executed. Additionally, failure orpotential failure modes, e.g., low voltage or over temperatureconditions, can be used to cause the safe harbor subroutine 378 to beexecuted. Typically, such a subroutine could cause a sequence ofcommands to be transmitted to set each microstimulator into a safecondition for the particular patient configuration, typically disablingeach microstimulator. Alternatively, the safe harbor condition could beto set certain stimulators to generate a prescribed sequence of drivepulses. Preferably, the safe harbor subroutine 378 can be downloadedfrom an external device, e.g., the clinician's programmer 172, into theprogram storage 310, a nonvolatile storage device. Additionally, it ispreferable that, should the programmable contents of the program storagebe lost, e.g., from a power failure, a default safe harbor subroutine beused instead. This default subroutine preferably stored in nonvolatilestorage that is not user programmable, e.g., ROM, that is otherwise aportion of the program storage 310. This default subroutine ispreferably general purpose and typically is limited to commands thatturn off all potential stimulators.

[0069] Alternatively, such programmable safe harbor subroutines 378 canexist in the implanted stimulators 100. Accordingly, a safe harborsubroutine could be individually programmed into each microstimulatorthat is customized for the environments of that microstimulator and asafe harbor subroutine for the SCU 302 could then be designated thatdisables the SCU 302, i.e. causes the SCU 302 to not issue subsequentcommands to other implanted devices 100.

[0070] FIGS. 10A and 10BD show two side cutaway views of the presentlypreferred construction of the sealed housing 206, the battery 104 andthe circuitry (implemented on one or more IC chips 216 to implementelectronic portions or the SCU 302) contained within. In this presentlypreferred construction, the housing 206 is comprised of an insulatingceramic tube 260 brazed onto a first end cap forming electrode 112 a viaa braze 262. At the other end of the ceramic tube 260 is a metal ring264 that is also brazed onto the ceramic tube 260. The circuitry within,i.e., a capacitor 183 (used when in a microstimulator mode), battery104, IC chips 216, and a spring 266 is attached to an opposing secondend cap forming electrode 112 b. A drop of conductive epoxy is used toglue the capacitor 183 to the end cap 112 a and is held in position byspring 266 as the glue takes hold. Preferably, the IC chips 216 aremounted on a circuit board 268 over which half circular longitudinalferrite slates 270 are attached. The coil 116 is wrapped around theferrite plates 270 and attached to IC chips 216. A getter 272, mountedsurrounding the spring 266, is preferably used to increase thehermeticity of the SCU 302 by absorbing water introduced therein. Anexemplary getter 272 absorbs 70 times its volume in water. While holdingthe circuitry and the end cap 112 b together, one can laser weld the endcap 112 b to the ring 264. Additionally, a platinum, iridium, orplatinum-iridium disk or plate 274 is preferably welded to the end capsof the SCU 302 to minimize the impedance of the connection to the bodytissue.

[0071] An exemplary battery 104 is described more fully below inconnection with the description of FIG. 11. Preferably, the battery 104is made from appropriate materials so as to provide a power capacity ofat least 1 microwatt-hour, preferably constructed from a battery havingan energy density of about 240 mW-Hr/cm³. A Li—I battery advantageouslyprovides such an energy density. Alternatively, an Li—I—Sn batteryprovides an energy density up to 360 mW-Hr/cm³. Any of these batteries,or other batteries providing a power capacity of at least 1microwatt-hour may be used with implanted devices of the presentinvention.

[0072] The battery voltage V of an exemplary battery is nominally 3.6volts, which is more than adequate for operating the CMOS circuitspreferably used to implement the IC chip(s) 216, and/or other electroniccircuitry, within the SCU 302. The battery voltage V, in general, ispreferably not allowed to discharge below about 2.55 volts, or permanentdamage may result. Similarly, the battery 104 should preferably not becharged to a level above about 4.2 volts, or else permanent damage mayresult. Hence, a charging circuit 122 (discussed in the parentapplication) is used to avoid any potentially damaging discharge orovercharge.

[0073] The battery 104 may take many forms, any of which may be used solong as the battery can be made to fit within the small volumeavailable. As previously discussed, the battery 104 may be either aprimary battery or a rechargeable battery. A primary battery offers theadvantage of a longer life for a given energy output but presents thedisadvantage of not being rechargeable (which means once its energy hasbeen used up, the implanted device no longer functions). However, formany applications, such as one-time-only muscle rehabilitation regimensapplied to damaged or weakened muscle tissue, the SCU 302 and/or devices100 need only be used for a short time (after which they can beexplanted and discarded, or simply left implanted as benign medicaldevices). For other applications, a rechargeable battery is clearly thepreferred type of energy choice, as the tissue stimulation provided bythe microstimulator is of a recurring nature.

[0074] The considerations relating to using a rechargeable battery asthe battery 104 of the implantable device 100 are presented, inter alia,in the book, Rechargeable Batteries, Applications Handbook, EDN Seriesfor Design Engineers, Technical Marketing Staff of Gates EnergyProducts, Inc. (Butterworth-Heinemann 1992). The basic considerationsfor any rechargeable battery relate to high energy density and longcycle life. Lithium based batteries, while historically used primarilyas a nonrechargeable battery, have in recent years appeared commerciallyas rechargeable batteries. Lithium-based batteries typically offer anenergy density of from 240 mW-Hr/cm³ to 360 mW-Hr/cm³. In general, thehigher the energy density the better, but any battery constructionexhibiting an energy density resulting in a power capacity greater than1 microwatt-hour is suitable for the present invention.

[0075] One of the more difficult hurdles facing the use of a battery 104within the SCU 302 relates to the relatively small size or volume insidethe housing 206 within which the battery must be inserted. A typical SCU302 made in accordance with the present invention is no larger thanabout 60 mm long and 8 mm in diameter, preferably no larger than 60 mmlong and 6 mm in diameter, and includes even smaller embodiments, e.g.,15 mm long with an O.D. of 2.2 mm (resulting in an I.D. of about 2 mm).When one considers that only about ¼ to ½ of the available volume withinthe device housing 206 is available for the battery, one begins toappreciate more fully how little volume, and thus how little batterystorage capacity, is available for the SCU 302.

[0076]FIG. 11 shows an exemplary battery 104 typical of those disclosedin the parent application. Specifically, a parallel-connectedcylindrical electrode embodiment is shown where each cylindricalelectrode includes a gap or slit 242; with the cylindrical electrodes222 and 224 on each side of the gap 242 forming a common connectionpoint for tabs 244 and 246 which serve as the electrical terminals forthe battery. The electrodes 222 and 224 are separated by a suitableseparator 248. The gap 242 minimizes the flow of eddy currents in theelectrodes. For this embodiment, there are four concentric cylindricalelectrodes 222, the outer one (largest diameter) of which may functionas the battery case 234, and three concentric electrodes 224 interleavedbetween the electrodes 222, with six concentric cylindrical separatorlayers 248 separating each electrode 222 or 224 from the adjacentelectrodes.

[0077] Accordingly, a preferred embodiment of the present invention iscomprised of an implanted SCU 302 and a plurality of implanted devices100, each of which contains its own rechargeable battery 104. As such, apatient is essentially independent of any external apparatus betweenbattery chargings (which generally occur no more often than once anhour). However, for some treatment regimen, it may be adequate to use apower supply analogous to that described in U.S. Pat. No. 5,324,316 thatonly provides power while an external AC magnetic field is beingprovided, e.g., from charger 118. Additionally, it may be desired, e.g.,from a cost standpoint, to implement the SCU 302 as an external device,e.g., within a watch-shaped housing that can be attached to a patient'swrist in a similar manner to the patient control unit 174.

[0078] The power consumption of the SCU 302 is primarily dependent uponthe circuitry implementation, preferably CMOS, the circuitry complexityand the clock speed. For a simple system, a CMOS implemented statemachine will be sufficient to provide the required capabilities of theprogrammable controller 308. However, for more complex systems, e.g., asystem where an SCU 302 controls a large number of implanted devices 100in a closed loop manner, a microcontroller may be required. As thecomplexity of such microcontrollers increases (along with its transistorcount), so does its power consumption. Accordingly, a larger batteryhaving a capacity of 1 watt-hour is preferred. While a primary batteryis possible, it is preferable that a rechargeable battery be used. Suchlarger batteries will require a larger volume and accordingly, cannot beplaced in the injectable housing described above. However, a surgicallyimplantable device within a larger sealed housing, e.g., having at leastone dimension in excess of 1 inch, will serve this purpose when used inplace of the previously discussed injectable housing 206. FIG. 12 showsan exemplary implantable housing 380 suitable for such a device.

[0079] While the invention herein disclosed has been described by meansof specific embodiments and applications thereof, numerous modificationsand variations could be made thereto by those skilled in the art withoutdeparting from the scope of the invention set forth in the claims. Forexample, a system including multiple SCUs, e.g., one external and oneinternal, is considered to be within the scope of the present invention.Additionally, while the use of a single communication channel forcommunication between one or more SCUs and the other implanted deviceshas been described, a system implemented using multiple communicationchannels, e.g., a first sonic channel at a first carrier frequency and asecond sonic channel at a second carrier frequency, is also consideredto be within the scope of the present invention.

We claim:
 1. A system for monitoring and/or affecting at least oneparameter of a patient's body, said system comprising: at least oneimplantable device operable to sense and/or stimulate a patient's bodyparameter in accordance with one or more controllable operatingparameters; and a system control unit for controlling said controllableoperating parameters, said system control unit comprising: a sealedelongate housing configured for implantation in a patient's body; asignal transmitter in said housing for transmitting command signals; asignal receiver in said housing for receiving status signals; and aprogrammable controller in said housing responsive to received statussignals for producing command signals for transmission by said signaltransmitter to said implantable devices.
 2. The system of claim 1wherein said sealed housing has an axial dimension of less than 60 mmand a lateral dimension of less than 6 mm suitable for injection intothe patient's body.
 3. The system of claim A1 comprising at least onesaid implantable device operable as a sensor and at least one saidimplantable operable as a stimulator and wherein said controller isresponsive to status data signals received from said sensor forgenerating said addressable command data signals to said stimulator toperform closed loop control of the operation of said stimulator.
 4. Thesystem of claim 1 wherein said system control unit additionallycomprises a power source contained within said sealed housing forproviding operating power to said data signal transmitter, said datasignal receiver, and said programmable controller.
 5. The system ofclaim 1 wherein said signal receiver includes a coil responsive tostatus signals defined by a modulated magnetic field.
 6. The system ofclaim 1 wherein said signal receiver includes a transducer responsibleto status signals defined by a modulated ultrasonic signal.
 7. Thesystem of claim 1 wherein said signal transmitter includes means fortransmitting command signals in the form of a modulated magnetic field.8. The system of claim 1 wherein said signal transmitter includes meansfor transmitting command signals in the form of a modulated ultrasonicsignal.
 9. The system of claim 1 wherein said system control unitadditionally includes: at least one electrode; sensor/stimulatorcircuitry; and wherein said sensor stimulator circuitry is configurableto generate a data signal representative of an electrical signalconducted by said electrode and/or supply a sequence of drive pulses tosaid electrode.
 10. The system of claim 1 wherein each of saidimplantable devices includes a power source having a capacity of atleast 1 microwatt-hour.
 11. The system of claim 10 wherein each saidimplantable device includes means for monitoring status of its powersource and said system control unit is configured to transmit commandsignals to each said implantable device and to responsively receivestatus signals corresponding to said power source status.
 12. The systemof claim 1 further including: program storage means in said housing forspecifying the operation of said programmable controller; and means tomodify said program storage means in response to signals received bysaid signal receiver.
 13. The system or claim 12 wherein said programstorage means includes means to cause said system control unit totransmit a programmable list of command signals to said implantabledevices.
 14. The system of claim 13 wherein said means to cause saidsystem control unit to transmit a programmable list of command signalsincludes: a magnetic sensor for generating a signal responsive to a DCmagnetic field; and wherein said programmable list of command signals istransmitted in response to said magnetic sensor signal.
 15. A systemcontrol unit configured for implantation in a patient's body forcontrolling/monitoring the operation of one or more other implantableaddressable devices, said system control unit comprising: a sealedelongate housing; a data signal transmitter for wireless transmission ofcommand data signals; a data signal receiver for wireless reception ofstatus data signals; a controller capable of accepting status datasignals from said data signal receiver and sending addressable commanddata signals to said data signal transmitter in response thereto tocontrol and/or monitor the operation of one or more other implantabledevices in accordance with one or more controllable operatingparameters; program storage means for specifying the operation of saidcontroller; and wherein said data signal transmitter, data signalreceiver, said controller, and said program storage means are disposedwithin said sealed housing.
 16. The system control unit of claim 15wherein said sealed housing has an axial dimension of less than 60 mmand a lateral dimension of less than 6 mm suitable for injection intothe patient's body.
 17. The system control unit of claim 15 additionallycomprising a power source contained within said sealed housing forproviding operating power to said data signal transmitter, said datasignal receiver, said controller, and said program storage means. 18.The system control unit of claim 15 wherein said data signal receiverincludes a coil responsive to a status data signal defined by amodulated magnetic field.
 19. The system control unit of claim 15wherein said data signal receiver includes a transducer responsive to astatus data signal defined by a modulated ultrasonic signal.
 20. Thesystem control unit of claim 15 wherein said transmitter includes meansfor transmitting a command data signal in the form of a modulatedmagnetic field.
 21. The system control unit of claim 15 wherein saidtransmitter includes means for transmitting a command data signal in theform of a modulated ultrasonic signal.
 22. The system control unit ofclaim 15 further including means to modify said program storage means inresponse to signals received by said data signal receiver.
 23. Thesystem control unit of claim 15 additionally including: at least oneelectrode; sensor/stimulator circuitry; and wherein said sensorstimulator circuitry is configurable to generate a data signalrepresentative of an electrical signal conducted by said electrodeand/or supply a sequence of drive pulses to said electrode.
 24. A systemfor monitoring and/or affecting at least one parameter of a patient'sbody, said system comprising: a system control unit positioned outsideof the patient's body comprising: means for providing wirelesstransmission of command data signals; means for providing wirelessreception of status data signals; and means capable of accepting statusdata signals from said data signal receiver and sending addressablecommand data signals to said data signal transmitter in response theretoto control and/or monitor the operation of one or more implantabledevices; and at least one addressable device configured for implantationin a patient's body responsive to said command data signals, saidimplantable devices selected from one or more of the following groups:stimulators having at least one electrode configured to produce anelectrical current for stimulating body tissue to affect a parameter ofthe patient's body; and sensors having at least one electrode configuredto produce a data signal corresponding to an electrical signal conductedby said electrode and representative of a parameter of the patient'sbody; and wherein each of said implantable devices includes a powersource having a power capacity of at least 1 microwatt-hour.
 25. Thesystem of claim 24 wherein said implantable devices include: at leastone stimulator and at least one sensor; and wherein said system controlunit is responsive to status data signals received from said sensor forgenerating said addressable command data signals to said stimulator toperform closed loop control of the operation of said stimulator.
 26. Thesystem of claim 24 wherein said groups of implantable devices furtherinclude transponders for transmitting a data signal related to a commandsignal received by said transponder.
 27. The system of claim 24 whereinsaid implantable devices include: at least one stimulator, at least onesensor and at least one transponder; and wherein said system controlunit is responsive to status data signals received from said sensor forgenerating said addressable command data signals to said stimulator toperform closed loop control of the operation of said stimulator.
 28. Thesystem of claim 27 wherein said status data signal received from saidsensor is received via said transponder.
 29. The system of claim 27wherein said stimulator is responsive to said command data signalsreceived via said transponder.
 30. The system of claim 24 wherein saidwireless reception means includes a coil responsive to a status datasignal defined by a modulated magnetic field.
 31. The system of claim 24wherein said wireless reception means includes a transducer responsiveto a status data signal defined by a modulated ultrasonic signal. 32.The system of claim 24 wherein said wireless transmission means includesmeans for transmitting a command data signal in the form of a modulatedmagnetic field.
 33. The system of claim 24 wherein said wirelesstransmission means includes means for transmitting a command data signalin the form of a modulated ultrasonic signal.